Step 1 - Access Website Management
After successfully logging into your Squarespace account, navigate to the [Website Management > Structure > Website Settings] configuration area.
Step 2 - Access the Search/Indexing Area
Next, click the Search/Indexing tab in the following page menu:
Step 3 - Add Site Description
In the Search/Indexing configuration area, scroll down to the Search Engine Parameters section and add your site description to the (optional) Description field. Then just make sure to click Update Information to save those changes:
Note: Changes made to your site description will not immediately update in search results for your pages. It will take Google and other search engines time to re-index your site contents with the new description.